1. Field of the Invention
The present invention relates in general to holders for holding sensors, and more particularly to holders of a type which holds a temperature sensor. More specifically, the present invention relates to holders for a temperature sensor which senses the temperature of a passenger cabin of motor vehicles.
2. Description of the Prior Art
In motor vehicles equipped with an automatic air conditioner, there are mounted various types of sensors which sense various conditions of a passenger cabin. Some of them are of a temperature sensor which senses the temperature of the passenger cabin.
Japanese Utility Model First Provisional Publication No. 56-73612 shows one holder for holding such a temperature sensor to a fixed member of a motor vehicle.
As is shown in FIG. 7 of the accompanying drawings, the holder shown in the publication is mounted to an instrument panel 1 exposed to a passenger cabin.
That is, the instrument panel 1 is formed with a bore into which a collar 12 is tightly mounted. The collar 12 has a flange part 16 exposed to the passenger cabin and an externally threaded part 18 exposed to the back side of the instrument panel 1. A grid member 17 is fitted into the flanged part of the collar 12. An annular member 13 is screwed onto the threaded part 18 of the collar 12. The annular member 13 has a passage formed therethrough. Thus, when an electric fan 5 is operated at the back side of the instrument panel 1, part of air in the passenger cabin is forced flow in the passage in the direction of the arrow.
A temperature sensor "S" is installed in the passage of the annular member 13 for sensing the temperature of air which passes through the passage. The sensor "S" shown by the publication is of a thermistor type which varies electric resistance with change of temperature.
Now, as is known, the latest motor vehicles tend to have, on the instrument panel, various heat generating devices such as radio, casette tape deck, compact disc player, lamped meters and the like. This means that the back side of the instrument panel tends to be heated considerably by such heat generating devices, due to poorly ventilated and small-sized space of the back side. Thus, when the sensor holder of the above-mentioned structure is applied to such instrument panel, the sensor holder is considerably heated and thus the air flowing therethrough is considerably heated before striking against the temperature sensor "S". In this condition, the temperature sensor "S" can not measure accurately the temperature of air in the passenger cabin.